1. Field of the Invention
The present invention relates generally to a plate material for printing, and more particularly to the plate material suitable for a printing method which comprises the steps of forming a liquid-attractive region (a latent image-forming region) selectively on a highly liquid-repellent surface of a printing plate, or of forming a liquid-repellent region (also, a latent image-forming region) selectively on a highly liquid-attractive surface of a printing plate, providing a recording liquid (for example, a liquid ink in a state of solution or dispersion) on the latent image-forming region, and then transferring the recording liquid to a plain paper or the like so as to produce an image.
2. Description of the Related Art
There has been an offset printing method by use of a waterless printing plate, as a representative printing method for use in forming an image by producing both a liquid-attracting region and liquid-repellent region on a surface of a printing plate. In practice, however, it is very difficult to incorporate all of the processes including a plate-making step and a printing step within a single apparatus in this offset printing method. This makes it difficult to have a compact apparatus in which the above steps can be performed.
For example, even in a case of relatively compact offset printing method, there are generally separate plate-making apparatus and printing apparatus. In addition, most materials for printing plate are usually pre-sensitive plates comprising a support and a photosensitive layer provided thereon and it is customary to discard these plates after single use for printing.
For the purpose of eliminating this defect of the offset printing method, there has been proposed a recording method and apparatus in which areas having a liquid-attractive property and areas having a liquid-repellent property can be generated on a recording medium in response to an image information and also in which the repeated usage of above recording medium is possible, that is, a printing process is reversible. The following are some of these.
After a charge is externally applied on a hydrophobic photo-electric conductive layer, the layer is exposed to light and a pattern can be formed which have both a hydrophobic portion and a hydrophilic portion on a surface of the layer. A water-soluble developing liquid adheres to only the hydrophilic portion and it is in turn transferred to a paper or the like, thus producing an image. Such method and apparatus are disclosed in Japanese Patent Publication Nos. 40-18992, 40-18993 and 44-9512, and Japanese Patent Laid-Open Application No. 63-264392.
In this method, ultraviolet light is irradiated to a layer including a material such as spiropyran or an azo dye so that a photochemical reaction of above dye occurs to make the layer hydrophilic. Such method and apparatus is described in xe2x80x9cJapanese Journal of Polymer Science and Technology (Kobunshi Ronbunshu)xe2x80x9d Vol. 37, No. 4 p287 (1980).
Japanese Laid-Open Patent Application No. 54-41902 describes a method whereby a portion to which a liquid ink adheres or does not adhere can be formed by physical transformation between an amorphous state and a crystalline state on a recording medium.
According to the above-mentioned method(1), after the water-soluble ink is transferred to the paper or the like, the hydrophilic portion is removed by removing the charge so that it is possible to record a next image. That is to say, one original plate (photo-electric conductive body) offers a repeated printing. However, since this method, in principle, employs electrophotographic process, it requires a long complicated process comprising charging, exposing, developing, transferring and discharging so that there are accompanying problems with making the apparatus based on the method (1) compact, in conjunction with reduction of a cost and maintenance-free operation.
With respect to method (2) described above, it is possible to freely control reversibility between hydrophilic and hydrophobic properties by selective irradiation of ultraviolet and visible light. However, since a quantum efficiency of reversibility is very low, a response time is extremely long and a recording rate is slow. In addition, there is provided the defect of an image stability. Therefore, this method (2) has not still reached a level of practical application.
Furthermore, although a information recording member which is used in the method (3) previously described has good stability after achieving a recording, there may be occasions that a structural transformation takes place due to temperature changes prior to the recording, thus giving rise to a stability problem. Additionally, a removal of a recorded information pattern requires means for applying a thermal pulse followed by rapid cooling so that it is difficult to perform frequent repetition of an image formation.
As described above, there has been a long-felt need to provide a printing method and printing material which are suitable for a compact printing apparatus. In order to accomplish this end, Japanese Laid-Open Patent Application Nos. 3-178478 and 9-52437 disclose a novel and useful recording method and recording medium therefor comprising a base member and a recording layer provided on thereon, having a characteristic in which a receding contact angle of the recording layer decreases against a liquid when the recording layer is heated or cooled in contact with the liquid. However, there is another problem that a surface of the above recording medium is likely to subjected to scratch so that a scratched portion tends to attract an ink, thereby generating a toning and an insufficient plate wear.
Accordingly, it is a general object of the present invention to provide a material for a printing plate in which the disadvantages of the aforementioned prior art are eliminated.
A more specific object of the present invention is to provide a material for the printing plate, having a good ink releasibilty and improved printing durability so that a number of good quality image can be obtained on a plain paper or the like.
The inventors of the present invention have performed much research and investigation regarding a material for printing plate in which the faults described for the conventional technologies have been eliminated.
The above objects of the present invention are achieved by a plate material for printing which comprises a substrate and a recording layer provided on the substrate, a surface of the recording layer having a changeable property of a receding contact angle, the recording layer comprising at least two polymers including a first polymer and a second polymer, the first polymer having the changeable property of the receding contact angle, wherein the second polymer has an oil-absorptive character defined as an area ratio determined by immersion test with a given solvent, and wherein the area ratio is in a range of from 110% to 200%.
According to the present invention, there is provided a plate material for printing for use in a recording method comprising in an arbitrary order the following steps of:
(a) bringing a contact material into contact with a surface of a recording layer, the surface having a property in which a receding contact angle decreases when the recording layer is heated in a state where the recording layer is in contact with a liquid, the contact material being selected from a liquid, a vapor and a solid which generates or changes to either a vapor or a liquid under condition of a temperature lower than a temperature at which the receding contact angle on the recording layer starts to decrease; and
(b) selectively heating the surface of the recording layer in response to an image information, whereby an area is formed with a receding contact angle in response to a heating temperature on the recording layer, the plate material comprising:
a substrate; and
the recording layer provided on the substrate, the surface of the recording layer having a changeable property of the receding contact angle, the recording layer comprising at least two polymers including a first polymer and a second polymer, the first polymer having the changeable property of the receding contact angle, wherein the second polymer has an oil-absorptive character defined as an area ratio determined by immersion test with a given solvent, and wherein the area ratio is in a range of from 110% to 200%.
The above objects of the present invention are also achieved by a plate material for printing for use in a recording method comprising the step of:
selectively heating a surface of a recording layer, the surface having a property in which a receding contact angle which was pre-decreased when the recording layer was heated in a state where the recording layer was in contact with a liquid changes into a original state when the recording layer is heated in an air in the absence of a liquid, whereby an area is formed with a receding contact angle in response to a heating temperature on the recording layer, the plate material comprising:
a substrate; and
the recording layer provided on the substrate, the surface of the recording layer having a changeable property of the receding contact angle, the recording layer comprising at least two polymers including a first polymer and a second polymer, the first polymer having the changeable property of the receding contact angle, wherein the second polymer has an oil-absorptive character defined as an area ratio determined by immersion test with a given solvent, and wherein the area ratio is in a range of from 110% to 200%.
An advantage of the present invention is the provision of a material for printing plate, the material having good ink releasibility so that a toning during press can be eliminated.
Furthermore, according to the present invention, it is possible to provide an improved printing plate which exhibits good printing durability.